| Year | Value | | 2022 | 1.6147644517108 | | 2021 | 1.6025879439863 | | 2020 | 1.6876017833783 | | 2019 | 1.5680132784018 | | 2018 | 1.4091766515593 | | 2017 | 1.3085654903679 | | 2016 | 1.264545875924 | | 2015 | 1.4790042022419 | | 2014 | 1.8938043611005 | | 2013 | 1.9570423918299 | | 2012 | 2.33372193259 | | 2011 | 1.5161305051084 | | 2010 | 1.8238795757871 | | 2009 | 1.5502576916036 | | 2005 | 1.8945992834878 | | 2003 | 1.5754231105397 | | 2002 | 1.5586028989376 | | 2001 | 1.626726770916 | | 2000 | 2.6280303617071 | | 1998 | 1.4047619047619 | | 1997 | 0.65052115266707 | | 1996 | 0.56659308314937 | | 1995 | 0.4955680902498 | | 1994 | 0.31796502384738 | | 1989 | 0.18108504398827 | | 1987 | 0.058086956521739 | | 1986 | 0.024396442185515 | | 1985 | 0.010903143739778 | | 1984 | 0.015024038461539 | | 1983 | 0.013478315464005 | | 1982 | 0.0086945777177713 |
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